A known internal combustion engine disclosed in JP2010-223212A (hereinafter referred to as Patent reference 1) includes a variable valve timing control apparatus configured with a driving-side rotating member synchronously driving with a crankshaft and a driven-side rotating member integrally and coaxially rotating with a camshaft.
According to the variable valve timing control apparatus disclosed in Patent reference 1, a vane is formed to be projected on an outer circumference of the driven-side rotating member. A fluid pressure chamber formed between the driving-side rotating member and the driven-side rotating member is divided by the vane to form an advanced angle chamber and a retarded angle chamber. A lock mechanism is configured such that a recessed portion is formed on the outer circumference of the driven-side rotating member and a lock member, corresponding to a lock piece disclosed in Patent reference 1, engaging and disengaging with the recessed portion is formed in a projectable and retractable manner from an inner circumference of the driving-side rotating member.
According to Patent reference 1, respective oil paths communicating with the advanced angle chamber and the retarded angle chamber are formed to shift, or change a relative rotational phase of the driving-side rotating member and the driven-side rotating member in an advanced angle direction and in a retarded angle direction. Further, an oil path is formed for unlocking the lock mechanism by supplying hydraulic oil to the recessed portion in a state where the lock mechanism is locked.
Particularly, the variable valve control apparatus disclosed in Patent reference 1 is configured to slightly leak the hydraulic oil while including an air inflow mechanism that positively discharges the hydraulic oil from the retarded angle chamber of the variable valve control apparatus when the internal combustion engine is stopped.
Comparing to a known variable valve timing control apparatus that leaves hydraulic oil in a fluid pressure chamber, the variable valve control apparatus including the air inflow mechanism as disclosed in Patent reference 1 easily shifts, or changes the relative rotational phase of the driving-side rotating member and the driven-side rotating member in a short time to establish the required relative rotational phase when the internal combustion engine is started. However, the air inflow mechanism disclosed in Patent reference 1 is configured to be closed by centrifugal force against the spring force when the variable valve control apparatus is rotated and to be opened by the spring force when the rotation of the variable valve control apparatus is stopped. Accordingly, the number of components is increased and the inflow of air may be impaired in case of operation failure of the air inflow mechanism.
When the operation of the air inflow mechanism is failed, the variable valve control apparatus including the air inflow mechanism as disclosed in Patent reference 1 leaves the hydraulic oil in the fluid pressure chamber. Thus, shifting, or changing the relative rotational phase of the variable valve control apparatus to an intermediate phase is time consuming. For example, when the internal combustion engine is started in a state where the relative rotational phase of the variable valve control apparatus is in the most retarded angle phase, changing the relative rotational phase to the intermediate phase is time consuming.
A need thus exists for an internal combustion engine which is not susceptible to the drawback mentioned above.